A&P 5

• bounded by double membrane
• contains materials needed to control ALL parts of the cell
• storage of the genetic material: DNA, packaged loose (euchromatin) when in use, packaged into tight structures (heterochromatin; chromosomes) when DNA must be divided between 2 daughter cells
• 3 forms of RNA (protein coding material) are made in the nucleus

• DNA makes RNA makes Protein
• DNA replicates itself
• DNA makes RNA by transcription, and the conversion of RNA code to Protein is translation
• DNA & RNA are the same basic structure,

• process of which DNA makes RNA
• same language, different format
• copying one form to another in the same language

• process of which RNA code converts to Protein
• different language: sequence of A, C, G, U
• converting information from one "language" to another

• DNA makes RNA (transcription)
• RNA makes Protein (translation)
• EXCEPTIONS: some viruses use RNA as their genetic material- reverse transcriptase (goes backward) RNA converts to DNA
• DNA is inserted into the host cell, this is destructive, damage to host cell DNA results in diseases, cancer, HIV (they use RNA as genetic material)

• enzyme, uses RNA as a template to make DNA
• after that step the usual sequence (DNA-> RNA->Protein) is followed

• DNA consists of 2 antiparallel strands (one goes up while the othe goes down) & RNA consists of 1 strand
• these #'s come from where 1 base is joined to the next along the deoxyribose-phosphate backbone
• DNA & RNA is always made & always read in a 5' to 3'(5 prime to 3 prime) direction
• DNA is visible throug light microscope when packaged into chromosomes during cell division, otherwise it's euchromatin: unspooled, "loose" DNA strands
• the base pairing of DNA & its directionality are the 2 most important features of this essential molecule

• the 5' carbon is where we start reading & where enzymes that work on DNA start their work
• the 3' end is where everything ends up

hydrogen bonded base pairs

• Region of DNA that codes for a protein
• (part of DNA that is made into protein)

Carries the code for a primary sequence of amino acids in protein

RNA transcribed from DNA has regions that are not used to code for protein synthesis, RNA must be edited to its final form BEFORE it’s shipped out of the nucleus

Enzyme that makes RNA from DNA template

• Promoter- starting point of RNA synthesis
• Terminator- stopping point of RNA synthesis

expressed region of DNA- made into protein

intervening region of DNA- NOT made into protein

in order to create mRNA from hnRNA (heterogeneous nuclear RNA), the intons must be sliced out and the exons stitched together (editing)

organelle that slices out introns & stitches together exons, made up of several small nuclear ribonucleoprotein particles, or snRNPs

structure formed (loops), the intron is cut out, and the ends of the exon are stitched together

"scissors & paste" in editing process

• when RNA polymerase touches down on DNA , it has to open up the DNA double helix, and start making RNA from a DNA template
• that hnRNA is then processed by snRNPs w/in the nucleus to form a final, edited transcript, which is officially called mRNA, passes through a pore in the nuclear envelope

• they are blood disorders
• they result from abnormal transcription and/or translation of alpha & beta-globin genes

• where promoter is found
• segment of DNA BEFORE the gene
• contains sequences that regulate transcription & translation

• where terminator is found
• segment of DNA AFTER the gene
• contains signals for the termination of transcription & also may have info about the stability of mRNA (some mRNAs need to hang around a long time & get translated over & over, while others should disappear in a puff of smoke after they're used once

• mRNA carries the coded message from nucleus to ribosome, ribosome is made up of ribosomal RNA & proteins
• together, rRNA & protein in ribosomes are a protein factory
• factory is supplied w/ amino acids for protein synthesis by tRNA that bring the correct amino acid for the next "word" in the genetic code

• tRNA- transfer RNA- "trucks" that take amino acids to growing protein strand
• mRNA-messenger RNA- carries coded message
• rRNA-ribosomal RNA- w/ proteins, forms ribosomes (protein factories): small & large subunits

• set of three ribonucleotides which will bind to the mRNA
• complementary sequence of tRNA bases

• ribosome finds start
• ribosome reads along mRNA & decodes mRNA to make polypeptide (immature protein)
• ribosome finds stop
• ribosome disassembles & translation stops

• 3 base pairs on mRNA coding for an amino acid
• (sequence of mRNA bases that codes for a protein)

• step1- ribosome attaches to mRNA
• step2- AUG(start codon) matches up to tRNA-methionine (*always start w/ AUG & always matched w/ mthionine)
• step3- next tRNA- amino acid arrives
• step4- peptide bond forms
• step5- ribosome shifts 3 mRNA bases (met-tRNA is released, open spot occupied by new amino acid-tRNA)
• step6- polypeptide chain grows
• step7- ribosome reaches stop codon polypeptide released

stem that carries amino acid

3 base sequence representing each amino acid

AUG

"umber" "amber" & "ochre"

1 start & 3 stop codons

"clowns" unique, oddballs

"gays" polar, charged

"boys" polar, uncharged

"girls" nonpolar

64 cominations code (makes 64 individual codons)

• change in the sequence of DNA which changes the mRNA made from the coding strand
• it's a general term for MUTATION

• noticeable changes in the organism
• if change in DNA (or mRNA) results in a change in the amino acid sequence, which then changes the function of the resulting protein

point mutation & frameshift mutation

• "swapping", they don't change the reading frame (sometimes they don't change protein sequence), they change one base
• 3 types: 1-silent mutations- no observable change (same), 2-missense mutations (sickle cell) change 1 amino acid to another (noticeable change, different), 3-nonsense mutations- change codon that codes for an amino acid to a stop codon, resulting in abnormally short protein (noticeable change, stop codon)

• change the reading frame
• types: either add (insertion mutation) or subtract (deletion mutation)

• 1- which strand of DNA is made into RNA
• 2- where the AUG (start) codon is found

• Sickle Cell Anemia (point mutation-missense)
• mutation of beta globin gene
• changes glutamate to valine
• sickling protects red blood cells against infection
• distribution of sickle cell mutation is a good match to the distribution of malaria-tropical regions

• messenger RNA
• allows us to make different proteins
• very unstable
• allows for transcriptional control of protein production
• made by RNA polymerase II

• ribosomal RNA
• more stable
• (mostly) made by RNA polymerase I
• combines w/ protein to form protein factories (ribosomes)
• makes RNA large & small units

• transfer RNA (shaped like cloverleaf)
• also stable
• made by RNA polymerase III
• "trucks" takes amino acids to "parking spaces" (P & A sites)

makes SnRNP (aka spliceosome)

DNA strand

• visible (only during mitosis) packaging of DNA & histones into X-shaped structures
• consists of 2 identical chromatids

• 2 identical halves of the chromosome, joined @ centromere (recall that the mitotic spindle attaches at the centromere and tears the 2 chromatids apart)
• each chromatid is one continuous DNA molecule

• special group of proteins
• positive charge to neutralize electrical charge of DNA, allows tighter packing

Mitotic phase (Mitosis (M phase) (prophase, metaphase, anaphase, & telophase) & Cytokinesis) & interphase (G₀, G1, S, & G2)

all cells make copies of themselves in the growing embryo, replace themselves: skin, bon marrow, intestinal lining, & others CANNOT divide after birth: muscle, heart muscle, and brain (nerves)

• (46 DNA molecules)
• cell duplicates organelles & cytoplasmic components
• in order to enter the next phase, S phase, cell in G₁ must pass a checkpoint
• process takes about 8-10 hours

• if the cell does NOT pass the checkpoint at G₁phase, then it goes to G₀phase
• or if the cell is quiescent (not actively dividing) the cell remains in G₀phase
• exs: brain cells, muscle cells, & heart muscle cells
• other cells (ex: liver & kidney) may wait in G₀phase for up to several years, but can prepare for division if needed

• DNA replication, so that it can be divided equally between daughter cells in mitosis
• process takes about 8 hours

• cell now carries double the amount of normal DNA (in G₁ it had 46 DNA molecules, now it has 92)
• duplication of centromeres
• there is another checkpoint, that needs to be passed, to get from G₂ to M phase
• process takes about 4-6 hours

• process of nuclear division
• actual active division of the cell
• interphase not a "true" phase of mitosis
• 4 stages w/in mitosis: prophase, metaphase, anaphase, & telophase
• last step in mitosis, CYTOKINESIS (process of cell division), cells must physically divide into 2 daughter cells
• diploids

• occurs in the S phase of cell cycle
• # of chromosomes is called "n" haploid
• 2 copies of each gene "2n" diploid
• DNA strands separated (one helicase(enzyme) unwinds DNA
• match up strands as they go down
• 2 strands of the DNA double helix are anti-parallel (1 runs 5'-->3'left to right & the other runs 5'-->3' right to left)
• DNA is only "built" 5'-->3'
• as DNA is replicated 2 strategies are used: leading strand & lagging strand

• deal w/ lagging strand
• they are smallish fragments of DNA being made in the required 5' to 3' direction
• okazaki fragments are filled in by DNA Ligase, one at a time, stitching the 5' to 3' strand together

• created on lower fork, RNA primers, DNA primase, & DNA polymerase working together
• okazaki fragments

• built continuously 5'-->3'
• DNA polymerase makes leading strand

enzyme that fills in gaps between the okazaki fragments, one at a time stitching the 5' to 3' strand together

uncoils (opens up) the helix

inserts swivel that keeps the intact double helix from getting supercoiled (keeps it from knotting) from spinning as replication proceeds

• 1st phase of mitosis
• DNA is tightly packed into chromosomes
• nuclear envelope breaks down
• mitotic spindle forms (which grows out of centrosome)

• 2nd phase of mitosis (middle phase(meta) of mitosis)
• everything in the parent cell lines up in the middle and microtubules of the mitotic spindle attach to anchors (centromeres) found in the middle of each chromosome
• karyotype test takes place here (to diagnose trisomy 21)

• 3rd phase in mitosis
• "ana"- backward
• phase where the contents of the 2 daughter cells move backwards away from eachother
• chromatids (arms of chromosomes) are torn apart into 2 equal pieces by the action of mitotic spindle
• they then back up & take their places on either end of the elongating cell

• end phase of mitosis
• mitosis is completed
• cleavage furrow appears in middle of parent cell
• as furrow deepens, cell is split into 2 daughter cells
• in each of daughter cells, nuclear envelopes reform & mitotic spindle comes apart

• "cell motion"
• daughter cells move apart
• process of cell division

• germ cells (sperm & eggs) they are haploid-carry only 1 copy of each gene
• they join @ fertilization
• when these germ cells join, the normal 2n amount of DNA is restored (n(23) + n(23) =2n(46))
• mechanism of cell division to evenly divide up the replicated 4n amount of DNA between four daughter cells
• to go from 4n to n, it requires 2 steps: meiosis I & meiosis II

• 1. meiosis I is a reduction division, so DNA content of each daughter cell is halved
• 2. crossing-over is a feature of Meiosis I, non-joined chromatids(from same region of same chromosome) "swap" & DNA is scrambled (gene swapping-mixing genetic material)

• aka reduction division
• splits the pairs
• crossing-over- non-sister chromatids swap genetic material
• content of each daughter cell is halved
• still goes through phases of Mitosis (PMAT)

• splits the chromosomes
• same steps basically but getting 4 daughter cells out of the 2 from meiosis I

• ensures "shuffling" of genetic material
• important benefit of sexual reproduction
• w/out it siblings would be identical
• tool used to determine the physical location of genes
• genes which are close together on the same chromosome rarely get separated during crossing over
• genes which are far apart on the same chromosome are more likely to be separated

• unit for measure (for crossing over) of genetic distance, physical distance between genes
• a 1% chance of crossing-over is called "1 centimorgan (1cM)"

• mitosis creates 2 daughter cells that are identical to the "parent", somatic(body) cells, splits pairs
• meiosis halves (4 daughter cells) the DNA content in meiosis I & then meiosis II resembles mitosis, germ cells, splits chromosomes

• haploid (N) use meiosis to divide- germ cells(gametes) reproductive cells, when they join they make a diploid embryo
• diploid (2N) use mitosis to divide- somatic cells (majority of body)

• those where inheriting one copy will give you a condition or disease
• capital letters

inherited characteristics that come in pairs

• those where inheriting one copy makes you a carrier and inheriting two copies will give you a condition or disease
• lower case letters

• child inherits one copy of a gene from mother and one from father- called alleles
• each parent's gametes are haploid- contain one allele each

• used to analyze mendelian genetics
• capital letters for dominant allele
• small letters for recessive allele

• lacking of skin pigmentation
• (aa on square) recessive recessive
• autosomal recessive genetic disease
• children have to receive 2 copies of the mutant gene to have albinism
• AA- unaffected Aa-unaffected carriers aa- affected (albino)

• a person needs 2 good copies of the hemoglobin gene to make normal red blood cells (HbA/HbA)
• one mutated copy produces sickle trait (HbA/HbS)
• 2 mutated copies produce sickle cell anemia (HbS/HbS)
• this is an example of a co-dominant trait- neither is recessive